1 Analog vs Digital Signals why do we human beings have to make signals anyway i To communicate yelling shouting flags ii To communicate even farther beacon tower reflecting the sunlight to make signals iii To communicate as far as we can How Telegraphs Invented some time around 1750 1850 by numerous inventors with a variety of different devices An electrical telegraph was independently developed and patented in the United States in 1837 by Samuel Morse Pros uses only dots and dashes can be viewed as 0 s and 1 s reliable after transmitting for a long distance 1 Telephones Invented some time between 1850 and 1900 uses a receiver which transforms acoustic pressures into electric signals analog signals and transforms it back to different loudness and frequencies of sound by the strength of the electric current Pros Straight forward way to transmit sound by electronic current which is easier to implement Cons Sensitive to all sorts of noise which could easily decrease the sound quality transmitted through the telephone Some Interesting Links How Analog and Digital Recording Works http communication howstuffworks com analog digital1 htm 2 Advantages of Digital Circuits Replication Error Correction Detection Miniaturization of Circuits Programmability Robust to Noise No need to worry about the recording media wearing out Think of your dad s old gramophone records or cassettes compare it with your CD DVD or MP3s 3 The bit bits Bytes and Words Ethernet Network in our Dorms 10M 100M 1000M Mb sec mega bits per sec CDs DVDs 700MB mega Bytes 4 7 GB Giga Bytes One Word 32 bits 4 Bytes does anyone know why they are 32 bits 4 Binary Decimal Conversion Signed Binary Numbers and Floating Points 2
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